You can find journal articles and other material using databases. Journals are academic magazines that are published regularly. Some journals are focused on news and trade e.g. Mathematics News Letter
Other journals publish original research. The most well regarded journals use a quality control procedure called peer-review. These are considered to contain material of the highest academic quality. An example of a peer-reviewed journal is: Acta Mathematica
Below is a list databases that are particularly relevant and useful for Mathematics. More databases covering other subject areas can be found on this a-z databases list.
SpringerLink
Full text access to over 2200 journals covering engineering, computing and mathematics as well as medical, health and life sciences. Includes 'Annals of Mathematics and Artificial Intelligence' and 'International Journal of Automotive Technology'.
Access is until the end of 2022.
ACM Digital Library
Association of Computing Machinery (ACM) digital Library. A full text database covering journal articles, conference proceedings, magazines and technical newsletters on the subjects of computing and information technology. Some content for mathematics for example ACM Transactions on Mathematical Software (TOMS).
arXiv.org
Hosted by Cornell University Library you can use this website to access e-prints in Mathematics, statistics, physics, computer science and related subjects.
Google Scholar
Google Scholar contains bibliographic records for a huge range of information sources across the full spectrum of subjects, including those for engineering, computing and mathematical subjects. There is no full text in this database, only bibliographic information and sometimes links to an external website where you may, or may not, be able to get the full text of the information source through Oxford Brookes University subscriptions.
IEEE Xplore Digital Library
The Institute of Electrical and Electronics Engineers (IEEE) publish many of the top journals in the areas of computer science, electronic engineering and telecommunications. You can access fulltext of IEEE and Institution of Engineering and Technology (IET) conference papers, journal articles, and IEEE standards back to 1988.
JSTOR
Full text access to a range of mathematical journals such as the Journal of the American Mathematical Society and the Annals of Mathematics. Most titles have a 3-5 year embargo.
ScienceDirect
ScienceDirect is a full text database from publisher Elsevier covering a range of science and mathematical and other subjects relevant titles include: Nonlinear Analysis: Hybrid Systems.
O'Reilly
A large collection of electronic books, videos and tutorials (Learning Paths). Although focussed on computing and information technology there is also material on mathematical topics such as algebra, combinatorics and calculus. Also accessible via iOS and Android apps.
Web of Science
Web of Science is a bibliographic database on a wide variety of interdisciplinary subjects including engineering, computing and mathematical subjects. There are some links to the full text via Oxford Brookes University subscriptions.
Academic Search Complete
Academic Search Complete is a large interdisciplinary database which includes some mathematics titles such as Acta Mathematica and both the Bulletin and the Proceedings of the London Mathematical Society. Some articles are full text, others just abstracts (summaries) of the full text.
